KR100205174B1 - Cinnamate which is photo-polymerization lc orientation material for va mode - Google Patents

Abstract

The citamate photopolymerizable alignment material of the present invention is a redirecting material in which a benzene ring having one or more fluorine groups is introduced into a benzene ring of a cinnamate side branch. By introducing a benzene ring having at least one fluorine group into the benzene ring of the cinnamate-based side branch, it is excellent in bonding strength with the liquid crystal polymer and can stabilize electro-optical characteristics at high temperature. In other words, by introducing a benzene ring having one or more fluorine groups to the benzene ring of the cinnamate side branch lowers the surface energy of the photopolymerizable alignment material polymer, thereby helping the liquid crystal polymer can be aligned vertically. Therefore, the cinnamate photopolymerizable alignment material of the present invention can obtain excellent characteristics by applying to VA Mode, which is a driving method of a new liquid crystal polymer.

Description

Cinamate Photopolymerization narrow liquid crystal alignment material for VA (Vertically Aligned) Mode

1 is a schematic view illustrating a liquid crystal alignment method by a rubbing process of a conventional TFT-LCD cell.

2 is an explanatory diagram showing a liquid crystal alignment method by optical alignment.

3 is an explanatory diagram showing the operation principle of the existing TN Mode liquid crystal.

4 is an explanatory diagram showing the operation principle of the VA Mode liquid crystal.

* Explanation of symbols for the main parts of the drawings

1 glass substrate 2 transparent conductive glass

3: liquid crystal molecule 4: polymer alignment film

5: rotating roller 6: rubbing cloth

9: copolymer type liquid crystal aligning film

[Field of Invention]

The present invention relates to a cinamate-based photopolymerization narrow liquid crystal aligning material for Vertically Aligned (VA) Mode of the present invention. More specifically, the present invention not only stabilizes the electro-optical properties at high temperature by introducing a functional group having excellent bonding strength with the liquid crystal in the benzene ring of the cinnamate side branch and the linkage thereof, but also replaces hydrogen of the benzene ring with at least one fluorine group. The present invention relates to a benzene ring cinnamate-based photopolymerizable alignment material which helps lower the surface energy to align the liquid crystals vertically.

Background of the Invention and Prior Art

Flat displays are thinner, thinner, and larger in size, and are increasingly replacing notebooks with notebook computer monitors. In particular, liquid crystal displays lead the flat-panel display market because they have the advantages of being portable and low in power consumption, and are expanding their applications from calculators and notebook computers to desktop computers and televisions.

Conventional methods for liquid crystal alignment include coating a heat-resistant polymer such as polyimide on a transparent conductive glass (2) by a printing method with a thickness of about 1000 kPa as shown in FIG. Is a method of rubbing the alignment film 4 while rotating the rotating ruler 5 wound with a rubbing cloth 6 such as nylon or rayon at high speed, which is called a rubbing process. As shown in FIG. 1, the rubbing process aligns the liquid crystal molecules with a predetermined pretilt angle θ in the polymer alignment film table.

However, the rubbing process causes mechanical scratches on the surface of the polymer alignment layer when rubbing, or generates high static electricity, which causes thin film transistors to break down and causes defects due to minute fibers generated in the rubbing cloth. It is becoming an obstacle. In addition, as the demand for a high-quality screen with a large area of 15 "or more is being studied, researches on orienting liquid crystals in order to obtain a good quality product quickly without rubbing are being actively conducted. This is a non-rubbing process. Representative examples of non-learning processes are M. Schadt (Jpn. J. Appl. Phys., Vol. 31. 1992.2155), Dae S. Kang (US Pat. No. 5,464,669), Yuriy Reznikov (Jpn. J). Appl. Pjys., Vol. 34. 1995. L1000), which is photo-alignment by photopolymerization, etc. Photo-alignment is the photosensitive group bound to the polymer by ultraviolet light linearly polarized by polarizer 7 It is a mechanism for forming the photopolymerizable liquid crystal alignment film 9. The side branches reacted in a predetermined direction are arranged in. The photoalignment material used in the patent and the paper is a polyvinyl alcohol (connamate) in polyvinyl alcohol (polyvinylaocohol). The double bond of cinnamate caused the cycloaddition reaction by the ultraviolet rays irradiated with UV-bonded alignment material, and only the cinnamate group coinciding with the polarization direction caused the cycloaddition reaction. When the optical alignment is used, a multi-domain pixel can be obtained using only a mask, and thus a liquid crystal display having a wide viewing angle can be obtained.

As liquid crystal displays have become larger in recent years, the use of personal computers, such as notebooks, has gradually expanded to households, such as wall-mounted TVs, requires large area, high definition, high quality, and wide viewing angles for liquid crystal displays. 3 is an explanatory diagram showing the operation principle of the conventional twisted nematic (TN) mode. In the uncharged state, the initial orientation is arranged with a constant pretilt angle so that light is emitted when the vertical polarizer is orthogonal to 90 °. When charged, the liquid crystals are arranged up and down to block light (Normally White). This conventional TN mode has a narrow viewing angle, which is problematic for many people to view at the same time. 4 shows the operating principle of the VA mode. In the initial state of no charge, the liquid crystals are arranged vertically and become normally black, which is a new mode of operation attracting attention recently because of a higher contrast ratio and a better viewing angle than the conventional TN mode. This mode does not have the disadvantage of completely changing the existing process like the In-Plane Switching (IPS) mode, and there is a commercial advantage that only the liquid crystal and the alignment layer need to be replaced. However, it is common conclusion that VA mode is slightly behind the viewing angle than IPS mode at this point when wide viewing angle is the biggest concern of LCD screen. VA mode cannot secure wide viewing angle better than multi-domain by pixel dividing by rubbing process using polyimide, so multi-domain using photopolymerization alignment material for VA Mode ) Will become an operation mode with high potential for practical use in the future.

As described above, unlike the conventional TN mode, the VA mode should be oriented vertically in a state in which no voltage is applied, so that the surface energy is minimized while maintaining the binding force and thermal stability of the alignment layer with the liquid crystals. A new structure in which the liquid crystal can be oriented perpendicular to the alignment film is advantageous. In the present invention, at least one hydrogen of the benzene ring is replaced with a fluorine group in the basic structure of the cinnamate photopolymerizable alignment material to lower the surface energy while maintaining thermal stability and bonding strength with the liquid crystal.

[Purpose of invention]

An object of the present invention is to provide a photopolymerizable alignment material for application to VA Mode.

Another object of the present invention is to provide a photopolymerizable alignment material having excellent thermal stability.

Still another object of the present invention is to provide a photopolymerizable alignment material having excellent alignment force.

Another object of the present invention is to provide a photopolymerizable alignment material having a low surface energy to favor vertical alignment.

Another object of the present invention is to combine the advantages of the high contrast ratio and wide viewing angle of VA Mode and the non-rubbing process of the optical orientation to produce high quality, high quality and wide viewing angle display of large area. It is to provide a photopolymerizable alignment agent that can be.

[Summary of invention]

The citamate photopolymerizable alignment material of the present invention is a redirecting material in which a benzene ring having one or more fluorine groups is introduced into a benzene ring of a cinnamate side branch. By introducing a benzene ring having at least one fluorine group into the benzene ring of the cinnamate-based side branch, it is excellent in bonding strength with the liquid crystal polymer and can stabilize electro-optical characteristics at high temperature. In other words, by introducing a benzene ring having one or more fluorine groups to the benzene ring of the cinnamate side branch lowers the surface energy of the photopolymerizable alignment material polymer, thereby helping the liquid crystal polymer can be aligned vertically. Therefore, the cinnamate photopolymerizable alignment material of the present invention can obtain excellent characteristics by applying to VA Mode, which is a driving method of a new liquid crystal polymer.

The cinnamate photopolymerization oriented material of this invention is represented by following structural formula (I):

Is a benzene group having at least one fluorine group.

In addition, the cinnamate photopolymerizable alignment material of the present invention also includes an alignment material in the form of a copolymer in which compounds having different side chains are bonded to one main chain in the compound of formula (I).

Detailed Description of the Invention

The cinnamate photopolymerizable alignment material of the present invention can lower the surface energy of the alignment material polymer while maintaining the thermal stability and the bonding force with the liquid crystal polymer by introducing a benzene ring having one or more fluorine groups into the benzene ring of the cinnamate side branch. This can help to align the liquid crystal polymer vertically. Therefore, the cinnamate photopolymerizable alignment material of the present invention can obtain excellent characteristics by applying to VA Mode, which is a driving method of a new liquid crystal polymer. In other words, by applying a cinnamate photopolymerizable alignment material with low surface energy to VA Mode to provide excellent thermal stability and orientation, and to favor vertical alignment, high contrast ratio, wide viewing angle, and non-rubbing. While maintaining the advantages of the process, it is possible to produce large area, high quality, high quality and wide viewing angle display.

The cinnamate photopolymerization type alignment material in the present invention has a structure of the following structural unit (I).

In the above formula, R1 is a group selected from the group consisting of a benben ring and an alkyl group represented by the following formula (II) capable of divalent bonding,

R2 is a zenene group having one or more fluorine groups and is selected from the group consisting of functional groups represented by the following formula (III),

Wherein X is at least one F, the remaining X is H, Y is -F, -CF3 or -C _n H _{2n + 1} (n is an integer from 1-6), and X is two or more F Y may be -H when substituted and R 3 is -H or -CH ₃ .

In addition, the cinnamate photopolymerizable alignment material of the present invention also includes an alignment material in the form of a copolymer in which compounds having different side chains in the compound of formula (I) are bonded to one main chain. The cinnamate photopolymerizable alignment material in the form of a copolymer is represented by the following formula (IV).

Wherein R1, R2 and R3 are as defined above and R1 ', R2' and R3 'are as defined in R1, R2 and R3, respectively, but R1 and R1' are not the same groups, and R2 and R2 'are also It is not the same group.

In the present invention, by introducing a benzene ring having one or more fluorine groups in the benzene ring of the side branch having a photoreaction cinnamate group to increase the thermal stability and bonding strength of the liquid crystal polymer, and lower the surface energy of the alignment material polymer Orientation of the liquid crystal polymer using a light deflector suitable for vertical alignment having light transmittance and excellent viewing angle characteristics. In this case, by replacing at least one fluorine in the benzene ring of the side branch, the surface energy is lowered more than the case of introducing only -F and -CF3 at the para position. It is applied to VA mode to secure wide viewing angle and at the same time make full use of the advantages of non-rubbing process.

The cinnamate photopolymerizable alignment material of the present invention can be applied to VA Mode to manufacture a VA Mode liquid crystal cell. The method of manufacturing a VA Mode liquid crystal cell includes dissolving a cinnamate photopolymerizable alignment material in an organic solvent, applying the dissolved alignment material to an ITO glass substrate to form an alignment film, drying the applied alignment film, and using a UV lamp. And irradiating the ultraviolet light linearly polarized by the polarizing plate on the surface of the alignment film at an angle of 0-90 ° for about 3-20 minutes to produce a liquid crystal alignment film.

In the present invention, organic solvents such as chlorobenzene, N-methylpyrrolidone (hereinafter abbreviated as "NMP"), gamma butyrolactone, and methoxy ethanol are prepared in order to manufacture a liquid crystal display cell using the photopolymerizable alignment agent. use. The concentration of these solutions is in the range of 1-10 wt%, the viscosity is in the range of 10-100 cP, and is applied at a thickness of 500-1,000 kPa by spin coating or printing. After drying for about 30 minutes after application, a polarizing ultraviolet ray linearly polarized using a polarizing plate using a UV lamp of 1KW intensity is irradiated on the surface of the alignment layer at an angle of about 0 ° -90 ° for about 3-20 minutes to arrange the polymer by photopolymerization. This induced foreign liquid crystal is aligned.

The present invention will be further illustrated by the following examples, which are only described for the purpose of illustrating the present invention and are not intended to limit the protection scope of the present invention.

Example 1

[Synthesis of mesogen with cinnamate]

0.1 mol (16.42 g) of parahydroxycinnamic acid was dissolved in 100 ml of water dissolved in 0.2 mol (8 g) of sodium hydroxide and 100 ml of dimethyl sulfoxide, and 0.1 mol (27.2 g) of pentafluorobenzoyl chloride was slowly added dropwise at 0 ° C. The mixture was stirred vigorously. The mixture was further reacted at room temperature for about 2 hours, and neutralized with dilute hydrochloric acid to pH = 6-7. The solid phase obtained was filtered and washed thoroughly with water. After drying completely in vacuo, recrystallization in ethanol gave pentafluorobenzoyloxycinnamic acid in yield 90%. 1.2 equivalents of thionyl chloride were added, and about 50 ml of methylene chloride was added, followed by reaction until a clear solution was obtained at room temperature. After the reaction, the solvent and thionyl chloride were removed in vacuo and thoroughly dried to give pentafluorobenzoylcinnamoylchloride.

[Synthesis of Photoalignment Material Having Cinnamate]

Polyhydroxystyrene having a molecular weight of 30,000 was dissolved in tetrahydrofuran (containing 1 equivalent of hydroxy group), and 1 equivalent of triethylamine was added thereto. One equivalent of pentafluorobenzoylcinnamoyl chloride synthesized in step 1 was dissolved in methylene chloride and reacted with a slow dropwise addition to the polymer solution at room temperature. After reacting for about 2-3 hours, the reactant was added dropwise to methol to precipitate. The precipitate obtained was filtered, washed thoroughly with water and methanol, and dried under high vacuum to give a polyhydroxystyrenyl-pentafluorobenzoyloxycinamate (hereinafter referred to as photoalignment material).

[Production of co-orientation VA Mode display cell]

The photo-alignment material was dissolved in NMP at a concentration of 1-10 wt%. This was spin-coated at a speed of 3,000 rpm on a thoroughly cleaned glass substrate coated with a transparent electrode. The coated glass substrate was dried at 200 ° C. for about 30 minutes to remove NMP, and 1KW ultraviolet light was linearly polarized using a polarizer to irradiate the upper and lower substrates once for 3 to 20 minutes. Photoreaction of two upper and lower glass substrates were bonded using an epoxy adhesive, and a negative type liquid crystal was injected into the bonded cells to prepare a photoaligned VA mode display cell. As a result, the pretilt angle was oriented at 87 ° -90 °, and the Contrast Ratio and Response Time were found to be equivalent to those of the cell by the rubbing process using polyimide, and the results are shown in Table 1.

Example 2

Synthesis of Photoalignment Copolymer

In the same manner as in Example (1), 0.1 mol (16.42 g) of parahydroxycinnamic acid was reacted with 0.1 mol (27.66 g) of 3,5-bistrifluoromethylbenzoyl chloride to give 3,5-bis Trifluoromethylbenzoyloxycinnamic acid was obtained which was reacted with 1.2 equivalents of thionylchloride to afford 3,5-bistrifluoromethylbenzoylchloride. The obtained mesogen was slowly added dropwise to the mesogenic pentafluorobenzoylcinnamoyl chloride obtained in Example 1 (1) in a polyhydroxystyrene solution having a molecular weight of 30,000 dissolved in tetrahydrofuran at the same time in a molar ratio of 1: 1. After reacting for 2-3 hours, a copolymerized orphan alignment material was obtained.

[Production of VA Mode Display Cell Using Photoalignment Copolymer]

Using the photo-alignment copolymer synthesized as in (1) above, VA Mode display cells were fabricated by irradiation of 1KW magnetic light as in Example 1 (3), and their characteristics were compared and investigated. The results were shown in Table 1.

Comparative Example: Fabrication of Polyimide VA Mode Test Cell by Rubbing Process

A polyimide alignment film made by Nippon Synthetic Rubber was spin-coated at 3000 rpm on a glass plate coated with a transparent electrode, and coated with a thickness of about 800 mm 3. After coating, the plate was dried at 200 ° C. for 1 hour using a heating plate. A rayon was wound around a 10 cm diameter roller to rub the polyimide surface once at a speed of 1000 rpm. The contact strength of the rayon fabric and the polyimide alignment layer was fixed at the instant the rayon fabric was in contact with the surface of the alignment layer. The rubbed upper and lower glass substrates were bonded in the same manner as in Example to prepare a polyimide VA Mode display cell by a rubbing process. The temperature was lowered to room temperature to measure and evaluate the electro-optical characteristics of the VA Mode display cell, and the results are shown in Table 1.

[Electro-optical Characteristic Evaluation Method]

※ Voltage / light transmittance (%) and contrast ratio were measured using LCD-5000.

※ pretilt angle: measured using the Crystal Rotation method.

All simple modifications or changes of the present invention can be easily carried out by those skilled in the art, and all such modifications or changes can be seen to be included in the scope of the present invention.

Claims (10)

Cinnamate photopolymerizable homopolymer aligning compound represented by the following general formula (I):

In the above formula, R ₁ is a group selected from the group consisting of a benzene ring and an alkyl group represented by the following formula (II) capable of divalent bonding,

R ₂ is a benzene group having at least one fluorine group, and R ₃ is H or CH ₃ . The cinnamate photopolymerizable homopolymer aligning compound according to claim 1, wherein R ₂ is selected from the group consisting of groups represented by the following formula (III):

Wherein X is at least one F, the remaining X is H, Y is -F, -CF ₃ or -CnH ₂ n + 1 (n is an integer from 1-6), and X is two or more F When substituted Y is -H, -F -CH ₃ or -CnH ₂ n + 1 (n is an integer from 1-6); Cinamate type photopolymerization copolymer alignment material compound represented by the following general formula (IV):

Wherein R ₁ and R ₂ and R ₃ are as defined in claim ₁ , R ₁ ′, R ₂ ′ and R ₃ ′ are as defined in R ₁ , R ₂ and R ₃ , respectively, and R ₁ and R 1 'Is not the same group and R ₂ and R ₂ are not the same group. Dissolving the photopolymerizable homopolymer berrant of claim 1 or 3 in an organic solvent for application in VA Mode; Applying the solution to an ITO glass substrate; Drying the coated alignment layer; And irradiating polarized ultraviolet rays to the surface of the dried alignment layer; A process for producing a cinnamate photopolymerizable liquid crystal alignment film, comprising the steps. The method of claim 4, wherein the organic solvent is selected from the group consisting of chlorovera, N-methyl picolatone, gamma butyrolactone, and methoxyethanol. The method of claim 4, wherein the coating step is performed by a spin coating method or a printing method. The method of claim 4, wherein the liquid crystal aligning agent solution dissolved in the organic solvent has a concentration of 1.0-10.0 wt% and a viscosity of 10-100 cps. The method for producing a cinnamate photopolymerizable homopolymer liquid crystal alignment film according to claim 4, wherein the alignment film has a thickness in the range of 500 to 1,000 GPa. A photo-aligned VA mode display cell comprising the steps of: bonding two photoreacted glass substrates of claim 4 to each other using an epoxy adhesive, and vacuum injecting the liquid crystal for VA Mode into the prepared cell. Way. Using a glass substrate mask of at least one of the upper and lower substrates of claim 4 to irradiate for 3 to 20 minutes at an angle of 0 ° ~ 90 ° in different directions to pre-tilt angle in different directions in two or more domains A method of manufacturing a photo-aligned multi-domain VA Mode display cell, characterized by manufacturing a liquid crystal alignment film to have.

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